Polyester composition and process for producing the same

ABSTRACT

The polyester composition giving formed articles, such as fibers or films, exhibiting improved color depth and clarity, when dyed, has characteristics comprising an intrinsic viscosity of not less than 0.60, a methyl terminal group concentration of less than 1.0 equivalent/ton, and a carboxyl group concentration of not more than 60 equivalents/ton, and contains 0.1 to 5 percent by weight of a metal-containing phosphorous compound produced by reacting a phosphate ester with an alkali metal and/or alkaline earth metal-containing compound in an amount of 0.5 to 3 parts by mole converted into the alkali metal per part by mole of said phosphate ester. Therein, the “amount converted into the alkali metal” is the double of the molar number of the alkaline earth metal, when the alkaline earth metal is used, or the sum of the double of the mole number of the alkaline earth metal and the mole number of the alkali metal, when the alkali metal and the alkaline earth metal are simultaneously used.

TECHNICAL FIELD

The present invention relates to a polyester composition. In moredetail, the present invention relates to a polyester composition whichcan easily form micropores on the surface of a formed article, whenformed into the shape of fiber or film, and can exhibit improved colordepth and clarity, when the formed article is dyed.

BACKGROUND ART

Polyesters have widely been used as synthetic fibers, because of havingmany excellent characteristics. However, the polyester fibers havedefects comprising inferior color development and inferior clarity,because of not having depth in color on coloration in comparison withnatural fibers such as wool or silk, cellulose fibers such as rayon oracetate fibers, acrylic fibers, and the like.

In order to solve the defects, the improvements of dyes and the chemicalmodifications of polyesters have been tried, but a sufficient effect hasnot been obtained by any of the improvements and the chemicalmodifications.

On the other hand, as a try for imparting unevenness to the surfaces ofpolyester fibers to give depth to a color on coloration has beenproposed, for example, a method for treating (alkali weight reduction)the fibers comprising a polyester containing polyoxyethylene glycoland/or a sulfonic acid compound with an aqueous solution of a basiccompound to form wrinkle-like micropores arranged in the axialdirections of the fibers.

However, a color depth-improving effect has not been recognized on thefibers obtained by this method, and the lowering in a visualconcentration has contrarily been recognized.

Namely, when the alkali weight reduction is insufficient in this method,the color depth-improving effect is never recognized, because theunevenness is formed only in the surface-near places of the fibers. Onthe other hand, when the alkali weight reduction is sufficient, thecolor depth is not improved, and a visual concentration is also lowered,because light is perhaps irregularly reflected. Even when the fibers arecolored in a deep color, the fibers appear whitish. In addition, thestrengths of the obtained fibers are remarkably lowered, and the fibersare easily fibrillated, whereby the fibers can not resist to theiremployments.

Further, proposed has been a method [JP-A 54-120728 (hereinafter, JP-Ameans “Japanese Unexamined Patent Publication”)] for subjecting a fibercomprising a polyester containing inorganic microparticles such assilica having particle diameters of not more than 80 nm to an alkaliweight reduction treatment to form irregular concaves and convexeshaving sizes of 0.2 to 0.7 μm and further form microconcaves andmicroconvexes having sizes of 0.05 to 0.2 μm in the concaves and theconvexes, thus improving the depth of color. However, a colordepth-improving effect is also insufficient by the method, and the fiberhas additionally a defect that the fiber is easily fibrillated, becauseof being made in such the extremely complicated uneven form.

In order to solve such the defects, proposed has been a method forproducing synthetic fibers having micropores, characterized by adding(a) a metal-containing phosphorous compound represented by thebelow-described formula (1) (wherein, R₁ and R₂ are each a monovalentorganic group, and R₁ and R₂ may be identical or different each other; mis 1, when M is an alkali metal, or ½, when M is an alkaline earthmetal) and (b) an alkaline earth metal in an amount of 0.5 to 1.2 molesper mole of said metal-containing phosphorous compound withoutpreliminarily reacting the compound (a) with the alkaline earth metal(b), at a step before a polyester synthesis reaction is finished,finishing the polyester synthesis reaction, melt-spinning the obtainedpolyester, and then treating the obtained fibers with an aqueoussolution of a basic compound to reduce a weight of not less than 2percent by weight. By the method, the polyester fiber having practicallyexcellent color depth can be obtained.

According to the method, insoluble particles can surely be produced inthe polyester in a homogeneously ultra fine particle-dispersed stateduring the reaction. However, the method has a problem that coarseparticles are liable to be produced by the slight difference of additionconditions such as a temperature on the addition of the additive and aspeed on the addition of the additive. Namely, since the once producedcoarse particles do not disappear, the coarse particles cause theclogging of a filter in a polymerization process, and the pressure riseof a pack and the breakage of fibers in a spinning process. Thereby, themethod has a problem that it is extremely difficult to perform acontinuous production by a batch type production method.

Furthermore, since the alkali metal or the alkaline earth metal is addedto the reaction system in this method, the metals accelerate thehydrolysis of the polyester component. Consequently, the carboxylterminal concentration of the polyester is enhanced, and the thermalstability of the resin composition is insufficient. Additionally, avicious circle that the carboxyl terminal groups further promote thecoagulation of the microparticles is caused.

In recent years, a direct esterification production method using adicarboxylic acid instead of the so-called organic carboxylate as anacid component has mainly been adopted, from reasons such as cost down,the decrease of impurities, and the improvement of the hue of thepolyester.

However, since carboxyl terminal groups do substantially not disappearfrom a raw material-charging time to a polycondensationreaction-starting time in this method, the employment of an alkali metalcompound or an alkaline earth metal compound as a raw material forforming a metal-containing phosphorous compound causes the formation andprecipitation of a metal carboxylate, a reaction failure, and theproduction of scaly coarse foreign matters in large amounts. Therefore,formation processes such as a spinning process can substantially not becarried out, and the fact is that such the composition is produced onlyfrom the so-called organic carboxylate as a raw material, thereby,enhancing the production cost.

DISCLOSURE OF INVENTION

An object of the present invention is to provide a polyester compositionwhich solves the above-described problems and gives formed products,such as fibers or films, exhibiting improved color depth and clarity,when dyed, and to provide a method for producing the polyestercomposition.

The polyester composition of the present invention capable of achievingthe above-described object and containing a metal-containing phosphorouscompound produced by reacting a phosphate ester with an alkali metaland/or alkaline earth metal-containing compound in an amount of 0.5 to 3parts by mole converted into the alkali metal per part by mole of saidphosphate ester, is characterized in that said polyester has anintrinsic viscosity of not less than 0.60, a methyl terminal groupconcentration of less than 1.0 equivalent/ton and a carboxyl terminalgroup concentration of not more than 60 equivalents/ton, and saidmetal-containing phosphorous compound has an average particle diameterof 0.01 to 0.1 μm and is contained in an amount of 0.1 to 5 percent byweight. Herein, the “amount converted into the alkali metal” means thedouble of the molar number of the alkaline earth metal, when thealkaline earth metal is used, or the sum of the double of the molenumber of the alkaline earth metal and the mole number of the alkalimetal, when the alkali metal and the alkaline earth metal aresimultaneously used.

They are preferable that not less than 80 percent by mole of therepeating units of the above-described polyester are ethyleneterephthalate units, that the polyester composition has a color b valueof not more than 2.5, and that a filtration pressure rise measured at a120 hour-elapsed time is less than 5 MPa/day, when said polyestercomposition is filtered through two orthogonally stacked filters eachcomprising a plain weave wire net having an inner diameter of 64 mm anda nominal aperture basic size of 0.026 mm (namely, corresponding to 500mesh) in accordance with JIS G3556 at a filtration rate of 33.3 g/minuteat a temperature of 290° C.

Further, a method for producing the polyester composition of the presentinvention, capable of achieving another object, is characterized byusing a dicarboxylic acid for an ester-forming acid component in anamount of not less than 80 percent by mole based on the ester-formingcomponent, when the polyester is produced from the ester-forming acidcomponents and an ester-forming diol component, and further by adding ametal-containing phosphorous compound produced by reacting a phosphateester with an alkali metal and/or alkaline earth metal-containingcompound in an amount of 0.5 to 3 parts by mole converted into thealkali metal per part by mole of said phosphate ester so as to give ametal-containing phosphorous compound content of 0.1 to 5 percent byweight, at a step on the way of said production process.

Furthermore, they are preferable that not less than 80 percent by moleof the above-described ester-forming acid component is terephthalicacid,

that the process for producing the above-described polyester comprises aprocess for esterifying the ester-forming acid component with theester-forming diol component in an esterification vessel, a process fortransporting a part of the produced oligomer liquid to apolycondensation reaction vessel to perform the polymerization, and aprocess for newly supplying the ester-forming acid component and theester-forming diol component to the oligomer left in the esterificationvessel to carry out the esterification,

that within 30 minutes after the finish of the transportation of theoligomer liquid to the above-described polycondensation reaction vessel,the transported oligomer liquid is mixed with the ester-forming diolcomponent at a temperature of not more than 50° C. in an amount of 2 to50 parts by weight per 100 parts by weight of the transported oligomerliquid, and then further with said metal-containing phosphorous compoundto carry out the polycondensation reaction,

that the temperature of the oligomer after the addition of theester-forming diol component is lowered to a temperature lower by 30 to50° C. than the melting point of a pentamer in the oligomer liquidtransported to the polycondensation reaction vessel, and

that an oligomer theoretical average polymerization degree calculatedfrom an ester-forming diol component/ester-forming acid component ratioafter the addition of the ester-forming diol component is not more than5.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, the present invention will be explained, while mainlyadopting a case that the shape of a formed article is a fiber, but it isa matter of course that the same effects can also be obtained in a casethat the shape of the formed article is one of other shapes, such as afilmy shape. Additionally, for example, “the diffused reflection oflight on the surface of a fiber” can be read in a different way as “thediffused reflection of light on the surface of a film”.

The polyester in the present invention is a linear saturated polyestersynthesized from an ester-forming acid component and an ester-formingdiol component. Herein, the ester-forming acid component in the presentinvention means a dicarboxylic acid and/or its ester-forming derivative,and the ester-forming diol component means a diol and/or itsester-forming derivative. In particular, a polyester synthesized from adicarboxylic acid and a diol is preferable, and it is especiallypreferable that terephthalic acid is the main raw material of theester-forming acid component. One or more other components may becopolymerized in response to a purpose within a range that physicalproperties as a general-purpose resin are not lost.

The above-described ester-forming acid component includes terephthalicacid, 2,6-naphthalenedicarboxylic acid, isophthalic acid,1,4-cyclohexyldicarboxylic acid, adipic acid, sebacic acid, phthalicacid, phthalic anhydride, 5-sodium sulfoisophthalic acid,5-tetrabutylphosphonium sulfoisophthalic acid, p-hydroxybenzoic acid,dimethyl terephthalate, dimethyl 2,6-naphthalenedicarboxylate, dimethylisophthalate, 1,4-cyclohexanedicarboxylic acid, dimethyl adipate,dimethyl sebacate, dimethyl phthalate, dimethyl 5-sodiumsulfoisophthalate, and dimethyl 5-tetrabutylphosphoniumsulfoisophthalate.

It is especially preferable to use terephthalic acid,2,6-naphthalenedicarboxylic acid, dimethyl terephthalate or dimethyl2.6-naphthalenedicarboxylate. However, it is undesirable that the rateof an organic carboxylate such as dimethyl terephthalate exceeds 20percent by mole, because the hue of the obtained polyester isdeteriorated due to an aldehyde and colorable decomposition productsproduced by the decomposition of the aldehyde. Therefore, it ispreferable that not less than 80 percent by mole of said ester-formingacid component is a dicarboxylic acid, especially terephthalic acid.

In addition, the ester-forming diol component includes ethylene glycol,1,3-propanediol, 1,4-butanediol, diethylene glycol, propylene glycol,2,2-dimethyl-1,3-propanediol, dipropylene glycol, 1,6-hexanediol,1,4-hexanedimethanol, dimethylolpropionic acid, poly(ethylene oxide)glycol, and poly(tetramethylene oxide) glycol. It is especiallypreferable to use ethylene glycol, 1,3-propanediol, or 1,4-butanediol.

It is especially preferable that not less than 80 percent by mole of therepeating units of a polyester are ethylene terephthalate units as thecombination of the ester-forming acid component with an ester-formingdiol component, because excellent physical properties can be realized.

In the polyester in the present invention, a polybasic carboxylic acidsuch as trimellitic acid, trimesic acid, trimellitic anhydride,pyromellitic acid, or monopotassium trimellitate, and/or a polyhydrichydroxy compound such as glycerol, sodium dimethylolethylsulfonate, orpotassium dimethylolpropionate may be copolymerized within a range forachieving the object of the present invention.

It is necessary that the intrinsic viscosity of the polyester in thepresent invention is not less than 0.60. When the intrinsic viscosity isless than 0.60, the physical properties of the obtained formed productsuch as a fiber are deteriorated, and the practicality of the polyesterhaving the low intrinsic viscosity is therefore poor. It is notnecessary that the upper limit of the intrinsic viscosity is especiallydetermined, but it is preferable that the upper limit of the intrinsicviscosity is not more than 1.20, because the polyester is easilyproduced and also easily formed into the formed product such as a fiber.

Further, it is necessary that the polyester in the present invention hasa methyl terminal group concentration of less than 1.0 equivalent/ton,preferably less than 0.1 equivalent/ton. When the methyl terminal groupconcentration is not less than 1.0 equivalent/ton, a colored substanceoriginated by the decomposition of the methyl terminal groups isproduced to yellow the polyester composition. Therefore, the methylterminal group concentration of not less than 1.0 equivalent/ton isundesirable in the present invention especially targeting the deepcolor.

Additionally, it is necessary that the carboxyl terminal groupconcentration of the polyester in the present invention is not more than60 equivalents/ton. The carboxyl terminal group concentration exceeding60 equivalents/ton is undesirable, because the thermal decomposition ofthe polyester is increased on the production of formed products such asfibers and further because the carboxyl terminal groups are recombinedwith the metal component in a remelting process for the production ofthe formed product from the pellets to produce coagulated foreignmatters insoluble in the polymer, thereby causing troubles such as thepressure rise of a pack.

Herein, the above-described inherent viscosity, methyl terminal groupconcentration, and carboxyl terminal group concentration are valuesrelated to the polyester, but are values measured, while a polyestercomposition is regarded as the polyester, when the polyester compositionsubstantially comprises the polyester and a metal-containing phosphorouscompound. When the polyester contains one or more other components assubstantial components, for example, in an amount of not less than 1percent by weight, the above-described values are values measured afterthe separation of the other components or values obtained by correctingthe measurement values of the polyester composition itself.

As the hue of the polyester composition of the present invention, it ispreferable that color b value is not more than 2.5. When the color bvalue exceeds 2.5, the deep color effect of the obtained formed productsuch as the fiber is liable to be poor.

It is necessary that the polyester composition of the present inventioncontains microparticles comprising the metal-containing phosphorouscompound produced by reacting the phosphate ester with the alkali metaland/or alkaline earth metal-containing compound.

Herein, it is especially not necessary that the phosphate ester islimited, and various phosphate esters such as monoeters, diesters andtrimesters can be used. Especially, trialkyl phosphates or triarylphosphates are preferable.

The alkali metal and alkaline earth metal in the present invention arepreferably Li, Na, Mg, Ca, Sr, and Ba, especially preferably Ca, Sr, andBa. The alkali metal and/or alkaline earth metal-containing compound inthe present invention may be any compound, when the compound reacts withthe above-described phosphate ester to produce the metal-containingphosphate compound. Concretely, the salts of organic carboxylic acidswith the alkali metal and/or alkaline earth metal are preferable.Especially, an acetate is preferable, because acetic acid produced bythe reaction can easily be removed.

When the phosphate ester is reacted with the alkali metal and/oralkaline earth metal-containing compound to produce the metal-containingphosphorous compound, it is necessary that 1 part by mole of thephosphate ester is reacted with 0.5 to 3 parts by mole, preferably 1.5to 3 parts by mole, especially preferably 2.5 to 3 parts by-moleconverted into the alkali metal, of the alkali metal and/or the alkalineearth metal-containing compound. When the phosphate ester is a monoesteror diester, it is preferable that the alkali metal and/or alkaline earthmetal-containing compound is reacted in an amount of not less than 2parts by mole converted into the alkali metal in the case of the formeror in an amount of not less than 1 part by mole converted into thealkali metal in the case of the latter.

The smaller rate of the alkali metal and/or alkaline earthmetal-containing compound than the range is often undesirable, becausethe phosphorous component deactivates a polyester polycondensationcatalyst to inhibit the polycondensation reaction, when saidmetal-containing phosphorous compound is dispersed in the polyester. Onthe other hand, when the rate of the alkali metal and/or alkaline earthmetal-containing compound is larger than the range, the depolymerizationof the polymer due to the alkali metal and/or alkaline earth metal isaccelerated, thereby being liable to cause problems such as theelongation of a reaction time and the coloration of the polymer.

The above-described metal-containing phosphorous compound is usuallyeasily obtained by thermally reacting the corresponding phosphate esterwith a prescribed amount of the corresponding alkali metal and/oralkaline earth metal-containing compound in a solvent. The solvent maysuitably be selected from known solvents, but it is most preferable touse a glycol used as a raw material for the targeted polyester.

When the above-described metal-containing phosphorous compound is addedto the polyester as the metal-containing phosphorous compound, it isestimated that the composition of, the metal-containing phosphorouscompound is maintained even in the polyester composition.

The content of the metal-containing phosphorous compound is 0.1 to 5percent by weight, preferably 0.2 to 3 percent by weight, especiallypreferably 0.3 to 2 percent by weight, based on the total weight of thepolyester composition. When the polyester composition having a contentof less than 0.1 percent by weight is formed into a formed article suchas a fiber or film and then dyed, a deed color effect is scarcelyobtained. On the other hand, a content exceeding 5 percent by weight isalso undesirable, because coarse foreign matters are increased.

The polyester composition of the present invention may contain a metalcompound catalyst, such as the compound of lithium, sodium, calcium,magnesium, manganese, zinc, antimony, germanium, or titanium, usuallyused on the production of polyesters, a phosphorous compound as ananti-coloring agent, inactive particles and an organic compound used formodifying the polyester, and the like, within ranges enabling theachievement of the purpose of the present invention.

Therein, it is necessary that the average particle diameter of themetal-containing phosphorous compound contained in the composition ofthe present invention is 0.01 to 0.1 μm, preferably 0.02 to 0.5 μm, fromthe viewpoint of the below-described micropore formability. The averageparticle diameter can be measured by a centrifugal sedimentation methodin accordance with JIS Z8823-1. The average particle diameter of lessthan 0.01 μm is undesirable, because, when the polyester composition isformed into fibers, the diameters of pores finally formed in the fibersare too small, thereby not accompanying the diffused reflection of lighton the surfaces of the fibers, and lacking the depth of a color, whendyed. On the other hand, the average particle diameter of more than 0.1μm is also undesirable, because the diameters of pores formed in thefibers are too large, thereby lacking the depth of a color, when dyed,being liable to coagulate a part of the metal-containing phosphorouscompound to form coarse particles, raising a pressure in a polymerfilter, enhancing the pressure of a pack in a spinning process, andinducing the breakage of fibers. Herein, the micropores mean manymicropores which are arranged on the surfaces of the fibers in thelongitudinal directions of the fibers and have minor axes of about 0.1to 2.0 μm and major axes of about 0.1 to 5.0 μm, when the polyestercomposition is formed into the fibers.

Since scarcely containing coagulated foreign matters, the polyestercomposition of the present invention has a characteristic that thepolyester composition can be filtered at an extremely low pressure riseof less than 5 MPa/day for the particle-containing polyestercomposition, when filtered at a temperature of 290° C. at a flow rate of33.3 g/minute through a 64 mm diameter filter obtained by orthogonallystacking two plain weave wire nets each having a nominal aperture basicsize of 0.026 mm in accordance with JIS G3556. When the similar pressurerise is further evaluated at an elapsed time of 120 hours, the pressurerise can still be maintained at a pressure rise of less than 5 MPa/day.Thereby, realized can be effects that the clogging of the filter and thepressure rise of a pack on the melt forming of the polyester compositionand troubles, such as fiber breakage and film breakage, on the processesare scarce. Herein, the pressure rise at an elapsed time of 120 hoursmeans a pressure rise value between an elapsed time of 120 hours and anelapsed time of 144 hours.

Next, an example of preferable production methods for obtaining thepolyester composition of the present invention will be explained indetail. Namely, the example is not a method for producing a polyesterand then blending the produced polyester with a metal-containingphosphorous compound, or the like, but a method for adding themetal-containing phosphorous compound related to the present inventionat a step on the way for producing the polyester. Herein, the method forproducing the polyester is often simply referred to as a method forproducing the polyester.

When the polyester is produced from an ester-forming acid component andan ester-forming diol component in the preferable production method, adicarboxylic acid, especially terephthalic acid, is used as theester-forming acid component in an amount of not less than 80 percent bymole of said ester-forming acid component, and a metal-containingphosphorous compound produced by reacting a phosphate ester with analkali metal and/or alkaline earth metal-containing compound in anamount of 0.5 to 3 parts by mole per part by mole of said phosphateester is added on the way of said production process to give a contentof 0.1 to 5 percent by weight.

Especially, preferable is a production method comprising a process foresterifying an ester-forming acid component with an ester-forming diolcomponent in an esterification vessel, a process for transporting a partof the produced oligomer liquid to a polycondensation reaction vessel tosubject the transported oligomer to the polycondensation reaction, and aprocess for newly supplying the ester-forming acid component and theester-forming diol component to the oligomer left in the esterificationvessel to carry out the esterification reaction. Herein, it ispreferable that the ester-forming acid component and the ester-formingdiol component newly supplied to the oligomer are equimolar to theester-forming acid component and the ester-forming diol component,respectively, contained in the oligomer liquid transported to thepolycondensation reaction vessel. The esterification in theabove-described esterification vessel and esterification reaction notonly means the direct esterification of the dicarboxylic acid with thediol, but may also include an ester interchange reaction from theester-forming acid component and the ester-forming diol component.

The weight ratio of the oligomer transported to the polycondensationreaction vessel to the oligomer left in the esterification vessel afterthe finish of the esterification reaction is preferably 1/5 to 5/1,especially preferably 1/2 to 2/1.

It is preferable in the above-described production method to supply thenot more than 50° C. ester-forming diol component to the oligomer liquidtransported to the polycondensation reaction vessel in an amount of 2 to50 parts by weight per 100 parts by weight of the transported oligomerwithin 30 minutes after the finish of the liquid transportation, add theabove-described metal-containing phosphorous compound, and thensubjecting the mixture to the polycondensation reaction. When 30 minutespasses after the transportation of the liquid, the quality deteriorationof the polymer and the lowering of productivity are liable to be causedby thermal deterioration and the like, because the total reaction timeis prolonged.

In addition, it is desirable that the not more than 50° C. ester-formingdiol component is added to the oligomer liquid transported to thepolycondensation reaction vessel to lower the inner temperature of thevessel. When the temperature of the ester-forming diol component exceeds50° C., it is difficult to lower the inner temperature of thepolycondensation reaction vessel, and it is also desirable from thepoint of safety that the hot ester-forming diol component is not used.

Furthermore, the oligomer is once depolymerized by the addition of theester-forming diol component of the specific temperature. It ispreferable that the temperature of the oligomer after the addition ofthe ester-forming diol component is in a lower temperature range by 30to 50° C. than the melting point of a pentamer in the oligomer. Herein,“the melting point of the pentamer in the oligomer” can be measured witha differential scanning calorimeter (DSC). When the temperature of theoligomer is lower than the temperature range and further when the innertemperature of the polycondensation reaction vessel is locally loweredby the addition of the ester-forming diol component, the mixture issolidified, thereby causing the damage of a stirring shaft and the like,or the reaction time is prolonged, thereby enhancing the risks ofthermal deterioration and productivity lowering. On the other hand, whenthe temperature of the oligomer is higher than the temperature range,the coagulation of the metal-containing phosphorous compound tends to beincrease on the addition of the metal-containing phosphorous compound.

The theoretical average polymerization degree of the oligomer termed inthe present invention is theoretically calculated from the ratio of theester-forming diol component to the ester-forming acid component in thereaction vessel, after the ester-forming diol component is added to theoligomer liquid transported to the polycondensation reaction vessel. Thetheoretical average polymerization degree of not more than 5, especially2 to 5 is preferable, because micropore formability is most excellent,when the obtained composition is formed and then subjected to thebelow-described treatment. An addition at a step exceeding 5 is oftenundesirable, because coagulated foreign matters are liable to beproduced perhaps due to the lowering of the solubility of themetal-containing phosphorous compound in the oligomer. The theoreticalaverage polymerization degree can be lowered to not more than 5 byadjusting the average polymerization degree of the oligomer before theaddition of the ester-forming diol component and the addition amount ofthe ester-forming diol component.

Within a range not inhibiting the object of the present invention, asmall amount of the ester-forming acid component may be added, when theabove-described ester-forming diol component is added.

The polyester composition of the present invention may be used forforming articles such as fibers or films as such, or used for producingthe so-called master batches, diluting the metal-containing phosphorouscompound concentration of the master batches with a polymer and thenusing the diluted product in a spinning process, in a film-formingprocess or in another forming process.

When said polyester composition is melt-spun into fibers, an ordinarymelt-spinning method for polyester fibers can arbitrarily be adoptedwithout needing a special spinning method. Herein, the spun fibers maybe solid fibers not having hollow portions or hollow fibers havinghollow portions. The cross-sectional outer shapes of the spun fibers andthe shapes of the hollow portions may be circular shapes or modifiedshapes. Further, the above-described polyester containing themetal-containing phosphorous compound and a polyester not containing themetal-containing phosphorous compound may together be used to makesheath-core type conjugate fibers or side-by-side type conjugate fiberseach having a two- or more-layered structure.

When micropores are formed on the surfaces of the obtained formedarticles such as the fibers, the formed articles exhibit improved colordepth and clarity, when dyed, and the abrasion durability of the formedarticles is also improved. A means for forming such the micropores maybe any means such as a physical means or a chemical means, but, when theformed articles are fibers, a means for brining the fibers into contactwith a basic compound to reduce the weights of the fibers is preferable.The contact of the fibers with the basic compound can easily be carriedout by, if necessary, subjecting the fibers to a treatment such as adrawing heating treatment or a false-twisting treatment, or furthermaking a fabric from the fibers, and then treating the fibers or thefabric with an aqueous solution of a basic compound.

The basic compound used herein includes sodium hydroxide, potassiumhydroxide, tetramethylammonium hydroxide, sodium carbonate, andpotassium carbonate. In particular, sodium hydroxide and potassiumhydroxide are preferable.

The concentration of the basic compound aqueous solution depends on thekind of the basic compound, treating conditions, and the like, but arange of 0.1 to 30 percent by weight is especially preferable. A rangeof the ordinary temperature to 100° C. is preferable as the treatingtemperature. The treatment is usually carried out in a range of 1 minuteto 4 hours.

Additionally, a weight reduced by the treatment of the fibers with theaqueous solution of the basic compound is not less than 2 percent byweight, preferably not less than 5 percent by weight, especiallypreferably not less than 10 percent by weight. By the treatment of thefibers with the aqueous solution of the basic compound, many microporesarranged in the fiber axial direction can be formed on the surfaces ofthe fibers and in the neighbors thereof, thereby exhibiting excellentcolor depth, when the fibers are dyed. The upper limit of the reducedweight is especially not limited, but the excessive reduced weight isliable to cause the deterioration of physical properties and thefibrillation of the fibers. Therefore, it is often needed to considerthe extent of the weight reduction. In many cases, 30 percent by weightis preferable as the upper limit.

EXAMPLES

The present invention will be explained in more detail hereafter withExamples. Herein, the measurements of characteristics in Examples werecarried out by the following methods, respectively. “Parts” in Examplesmeans parts by weight.

(Average Particle Diameter)

The average particle diameter was measured with CAPA-500 manufactured byHoriba Seisakusho Co. in accordance to JIS Z8823-1.

(Inherent Viscosity (η))

A sample was dissolved in a solvent mixture of 40 parts by weight of1,1,2,2-tetrachloroethane with 60 parts by weight of phenol and thenmeasured by an established method at 35° C.

(Filtration Pressure Rise of Polyester Composition)

A filtration pressure rise rate was evaluated for evaluating thepressure rise on the filtration of the polyester composition, asdescribed below.

A polymer metering feeder was attached to the melted polymer exit sideof a small single screw type extruder, and further orthogonally stackedtwo filters each comprising a plain weave wire net having an innerdiameter of 64 mm and a nominal aperture basic size of 0.026 mm inaccordance with JIS G3556 were attached to the exit side. Then, thetemperature of the melted polymer was constantly controlled to 290° C.,and the melted polymer was continuously filtered at a polymer flow rateof 33.3 g/minute for 24 hours. A pressure rise value on the filtrationfilter entrance side for 24 hours was defined as a filtration pressurerise rate 1. Further, the filtration operation was continued, and apressure rise value from 120 hour time to 144 hour time was defined as afiltration pressure rise rate 2. The filtration pressure rise rate 2 is“filtration pressure rise” of the present invention.

(Color b Value)

The color b value was measured with a color-difference meter CR-300manufactured by Minolta limited.

(Depth of Color)

Deep color degree (K/S) was used as a scale for showing the depth ofcolor. The spectral reflection factor of a sample fabric was measuredwith RC-330 type recording spectrophotometer manufactured by ShimadzuCo., and the deep color degree was then determined from the followingequation of Kubelka-Munk. The determined value shows that the larger thevalue is, the larger the deep color effect is.K/S=(1−R)²/2RTherein, R, K and S represent a reflectance, an absorption coefficient,and a scattering coefficient, respectively.(Abrasive Discoloration Resistance)

A test fabric was subjected to 200 surface-abrading operations under aload of 500 g, while using a Gakushin type surface abrasion machine fortesting fastness to rubbing and using a georgette comprising 100%polyethylene terephthalate as a rubbing cloth. The extend ofdiscoloration was judged with a gray scale for discoloration. When theabrasion is greatly low, the test fabric was classified as the firstgrade. When the abrasion is extremely high, the test fabric wasclassified as the third grade. Only the first grade is placed at a levelto be supplied for practical uses.

Reference Example

(Synthesis of Metal-containing Phosphorous Compound)

A 7.5 percent by weight ethylene glycol solution of calcium acetateproduced by Wako Pure Chemical Industry Ltd. was added to a 5.0 percentby weight ethylene glycol solution of trimethyl phosphate produced byDaihachi Chemical Industry (Ltd.) at ordinary temperature with stirringat a rate of 1.5 parts by mole of the calcium acetate per part by moleof the trimethyl phosphate, and then maintained at 150° C. for 2.5 hoursto obtain the metal-containing phosphorous compound solution.

Example 1

86 Parts by weight of terephthalic acid was esterified with 40 parts byweight of ethylene glycol in an esterification vessel by a conventionalmethod to obtain the oligomer. 86 Parts by weight of terephthalic acidand 40 parts by weight of ethylene glycol were supplied to the oligomerfor 65 minutes and subjected to an esterification reaction at 245° C.Then, 0.045 part by weight of antimony trioxide was added, and, 20minutes later, the oligomer liquid in a molar amount equivalent to themolar amount of the oligomer produced from the added terephthalic acidand the added ethylene glycol was transported to a polycondensationreaction vessel. After the finish of the transportation, 10 parts byweight of 20° C. ethylene glycol was supplied to the polycondensationreaction vessel and then stirred and maintained for five minutes. Whenthe inner temperature became 210° C., the metal-containing phosphorouscompound solution obtained in Reference Example was added in an amountof 0.5 part by weight converted into the trimethyl phosphate. When themetal-containing phosphorous compound solution was added, the meltingpoint of the oligomer was 200° C., and the main component of theoligomer was a trimer. Subsequently, the oligomer was heated up to 290°C. and polycondensed under a high vacuum of not more than 0.03 kPa toobtain the polyester having an inherent viscosity of 0.64, which waspelletized. The obtained polyester pellets had a color b value of 0.0, amethyl terminal group concentration of not more than 0.1 equivalent/ton,and a carboxyl terminal group concentration of 51 equivalents/ton. Theaverage particle diameter of the metal-containing phosphorous compoundwas 0.03 μm. The content of the metal-containing phosphorous compoundwas 0.5 percent by weight.

The pellets were dried at 140° C. for 6 hours and then melt-spun througha spinneret having 36 perforated circular spinning nozzles each having anozzle diameter of 0.3 mm at 290° C. for 120 hours. The obtained undrawnfilaments were drawn at a draw ratio of 3.5 to obtain 83 dtex/36 fildrawn filaments.

A pressure rise in the spinning process was 0.1 MPa/day, and filamentbreakage rates in the spinning process and in the drawing process werenot more than 1%, respectively. The values were comparable with those,when the polyester not containing the metal-containing phosphorouscompound of the present invention was spun and drawn.

Herein, the spinning filament breakage rate among the filament breakagerates was obtained by recording the number of spinning filamentbreakages occurred during the operation of a spinning machine exceptfilament breakages caused by artificial or mechanical factors and thencalculating the spinning filament breakage rate (%) with the followingequation.

Spinning filament breakage rate (%)=[the number of filamentbreakages/(the number of operated winders×the number of doffingoperations)×100

-   -   (wherein, the number of the doffing operations is the number of        undrawn filament packages each wound up to a specified amount        (10 kg)).

Further, the drawing filament breakage rate was obtained by recordingthe number of drawing filament breakages occurred during the operationof a drawing machine except filament breakages caused by artificial ormechanical factors and then calculating the drawing filament breakagerate (%) with the following equation.

Drawing filament breakage rate (%)=[the number of filamentbreakages/(the number of operated spindles×the number of doffingoperations)×100

-   -   (wherein, the number of the doffing operations is the number of        drawn filament packages each wound up to a specified amount (2.5        kg)).

The obtained drawn filaments were subjected to a hard twist operation atan S-twist of 2,500 T/m or a Z-twist of 2,500 T/m, and then subjected toa steaming treatment at 80° C. for 30 minutes to fix the twists, thusobtaining the S-twist hard twisted yarn or the Z-twist hard twistedyarn. Said twist-fixed hard twisted yarns were woven at a warp densityof 47 yarns/cm and at a weft density of 32 yarns/cm to produce the crepegeorgette woven fabric in which units each comprising two S-twist hardtwisted yarns and units each comprising two Z-twist hard twisted yarnswere alternately arranged.

The obtained gray fabric was relaxed with a rotary washer at a boilingtemperature for 20 minutes to crepe the fabric, preset by a conventionalmethod, and then treated with a 3.5 percent by weight sodium hydroxideaqueous solution at a boiling temperature to obtain the fabric having areduction rate of 20 percent by weight. It was confirmed with anelectron microscope that many micropores arranged in the fiber axialdirection and having minor axes of 0.1 to 0.5 μm and major axes of 0.5to 0.8 μm were formed on the fiber surfaces of the reduced fabric.

The alkali-reduced fabric was dyed with 15% owf of Dianoix Black HG-FS(produced by Mitsubishi Chemical Co.) at 130° C. for 60 minutes, andthen reduced and washed with an aqueous solution containing 1 g/L ofsodium hydroxide and 1 g/L of hydrosulfite at 70° C. for 20 minutes toobtain the black dyed fabric. The color depth of the obtained blackfabric and its abrasive discoloration resistance after 200 rubbingoperations are shown in Table 1.

Otherwise, the above-described “filtration pressure rise of polyestercomposition” test was carried out, and a filtration pressure rise rate 1and a filtration pressure rise rate 2 were measured. The results areshown in Table 1.

Furthermore, after the oligomer was transported to the polycondensationreaction vessel, 86 parts by weight of terephthalic acid and 40 parts byweight of ethylene glycol were supplied to the oligomer left in theesterification vessel for 65 minutes, and esterified at 245° C. Aprescribed amount of antimony trioxide was added. 20 Minutes later, theoligomer in a molar amount equivalent to that of the oligomer obtainedfrom the additionally supplied terephthalic acid and the additionallysupplied ethylene glycol was transported to the polycondensationreaction vessel, and polymerized. Then, the polyester pellets wereobtained similarly as described above. These operations were repeated,and the same results as described above were obtained.

Comparative Example 1

100 Parts by weight of dimethyl terephthalate and 70 parts by weight ofethylene glycol were subjected to an ester interchange reaction in thepresence of 0.038 part by weight of manganese acetate-tetrahydrate as acatalyst by a conventional method, and the obtained oligomer was mixedwith tribasic calcium phosphate (Ca₃(PO₄)₂) having an average particlediameter of 0.5 μm in an amount of 0.5 percent by weight based on theweight of the obtained polyester composition at 260° C., reacted for 15minutes, mixed with 0.045 part by weight of antimony trioxide, furtherreacted for 5 minutes, heated to 290° C., and then polycondensed under ahigh vacuum of not more than 0.03 kPa to obtain the polyester having aninherent viscosity of 0.64. The polyester was pelletized.

The obtained pellets were treated similarly to those in Example 1. Theresults are shown in Table 1. Approximately elliptic micropores existedon the surface of the reduced fabric so that the major axes of themicropores are parallel to the fiber axes. However, the formation oflarge holes having diameters of not less than 5 μm was simultaneouslyrecognized at a rate of 30% based on the total number of the micropores,and it was clarified that a deep color effect was poor.

Additionally, a methyl terminal group concentration was 3.0equivalents/ton. A pressure rise in the spinning process was 1.5MPa/day, and filament breakage rates in the spinning process and in thedrawing process were 2% and 5%, respectively.

Comparative Example 2

Operations were carried out similarly to those in Example 1 except that1 part by weight of p-methoxybenzoic acid as a spinneret foreign matterinhibitor was added at the same time as charging terephthalic acid, andfurther except that the metal-containing phosphorous compound solutionobtained in Reference Example was added without adding ethylene glycolto the oligomer liquid transported to the polycondensation reactionvessel (the temperature of the oligomer was 240° C.). The results areshown in Table 1. Elliptic micropores existed on the fiber surface ofthe reduced fabric. However, the formation of large holes havingdiameters of not less than 5 μm was simultaneously recognized, and itwas clarified that a deep color effect was poor.

Additionally, a methyl terminal group concentration was not more than0.1 equivalent/ton, and a carboxyl terminal group concentration was 63equivalents/ton.

Further, a pressure rise in the spinning process was 1.8 MPa/day, andfilament breakage rates in the spinning process and in the drawingprocess were 2% and 4%, respectively.

Examples 2 and 3

Operations were carried out similarly to those in Example 1 except thatthe metal-containing phosphorous solution obtained in Reference Examplewas added in an amount of 0.5 part by weight converted into trimethylphosphate, when a stirring and maintaining time was changed after thesupply of 10 parts by weight of 20° C. ethylene glycol to apolycondensation reaction vessel to give an inner temperature of 190° C.(Example 2) or 220° C. (Example 3), respectively. The results are shownin Table 1.

TABLE 1 Com- Com- parative parative Exam- Exam- Exam- Exam- Exam- ple 1ple 1 ple 2 ple 2 ple 3 Polyester composition Microparticle average 0.030.50 0.07 0.02 0.07 particle diameter μm Micropartide content 0.5 0.50.5 0.5 0.5 % Inherent viscosity 0.64 0.64 0.64 0.64 0.64 dL/g Carboxylterminal 51 45 63 45 53 groups equivalents/ton Methyl terminal not 3.0not not not groups equivalents/ton more more more more than 0.1 than 0.1than 0.1 than 0.1 Filtration pressure 0.10 1.30 1.20 0.10 0.30 rise 1MPa/day Filtration pressure 0.20 5.10 5.50 0.20 0.30 rise 2 MPa/dayEvaluation of processes for producing filaments Pressure rise during 0.11.5 1.8 0.1 0.2 spinning MPa/day Spinning filament 1 2 2 1 1 breakagerate Drawing filament 1 5 4 0 1 breakage rate Evaluation of dyeing Depthof color (K/S) 26.0 24.5 24.4 26.2 25.8 Abrasive discoloration 1 2 1 1 1resistance grade

Examples 4 to 7

Operations were carried out similarly to those in Example 1 except thatthe metal-containing phosphorous solution was added so that the contentof microparticles in the obtained composition was described in Table 2and further except that the polycondensation reaction was carried outuntil giving an inherent viscosity described in Table 2. But, in Example6 was used a metal-containing phosphorous compound solution obtained byusing barium acetate instead of calcium acetate in Reference Example, asthe metal-containing phosphorous compound.

TABLE 2 Example 4 Example 5 Example 6 Example 7 Polyester compositionMicroparticle average 0.03 0.03 0.08 0.03 particle diameter μmMicroparticle content % 0.5 0.2 2.0 0.5 Inherent viscosity dL/g 0.640.63 0.62 0.68 Carboxyl terminal groups 53 48 45 46 equivalents/tonMethyl terminal groups not more not more not more not moreequivalents/ton than 0.1 than 0.1 than 0.1 than 0.1 Filtration pressurerise 1 0.05 0.30 0.40 0.10 MPa/day Filtration pressure rise 2 0.10 0.700.90 0.30 MPa/day Evaluation of processes for producing filamentsPressure rise during 0.1 0.5 0.5 0.1 spinning MPa/day Spinning filamentbreak- 0 2 2 2 age rate Drawing filament break- 0 2 3 0 age rateEvaluation of dyeing Depth of color (K/S) 25.6 26.8 25.3 26.1 Abrasivediscoloration 1 1 1 1 resistance grade

INDUSTRIAL APPLICABILITY

According to the present invention, characteristic micropores can easilybe formed on the surface of a formed article such as a fiber or a film.Therefore, provided is a polyester composition which can exhibitimproved color depth and clarity, when dyed. Moreover, the color depthand the clarity have excellent frictional resistance. Furthermore, sincescarcely containing foreign matters, the composition has characteristicsthat the clogging of a filter, the pressure rise of a pack on blendingand on the melt-forming of fibers, films, and the like, and troubles onprocesses, such as filament breakages and film breakages, are scarce.

1. A polyester composition comprising a polyester and a metal-containingphosphorous compound produced by reacting a phosphate ester with analkali metal and/or alkaline earth metal-containing compound in anamount of 0.5 to 3 parts by mole converted into the alkali metal perpart by mole of said phosphate ester, wherein said polyester has anintrinsic viscosity of not less than 0.60, a methyl terminal groupconcentration of less than 1.0 equivalent/ton and a carboxyl terminalgroup concentration of not more than 60 equivalents/ton, and saidmetal-containing phosphorous compound has an average particle diameterof 0.01 to 0.1 μm and is contained in an amount of 0.1 to 5 percent byweight.
 2. The polyester composition according to claim 1, wherein notless than 80 percent by mole of the repeating units of the polyester areethylene-terephathlate units.
 3. The polyester composition according toclaim 1 or claim 2, wherein the polyester composition has a color bvalue of not more than 2.5.
 4. The polyester composition according toclaim 1 or claim 2, wherein a filtration pressure rise measured at a 120hour-elapsed time is <5 MPa/day, when said polyester composition isfiltered through two orthogonally stacked filters each comprising aplain weave wire net having an inner diameter of 64 mm and a nominalaperture basic size of 0.026 mm in accordance with JIS G3556 at afiltration rate of 33.3 g/minute at a temperature of 290° C.
 5. A methodfor producing a polyester composition, characterized by using adicarboxylic acid for an ester-forming acid component in an amount ofnot less than 80 percent by mole based on the ester-forming component,when the polyester is produced from the ester-forming acid component andan ester-forming diol component, and further by adding ametal-containing phosphorous compound produced by reacting a phosphateester with an alkali metal and/or alkaline earth metal-containingcompound in an amount of 0.5 to 3 parts by mole converted into thealkali metal per part by mole of said phosphate ester so as to give ametal-containing phosphorous compound content of 0.1 to 5 percent byweight, at a step on the way of said production process.
 6. The methodfor producing the polyester composition according to claim 5, whereinthe dicarboxylic acid is terephthalic acid.
 7. The method for producingthe polyester composition according to claim 5, wherein the process forproducing the polyester comprises a process for esterifying theester-forming acid component with the ester-forming diol component in anesterification vessel, a process for transporting a part of the producedoligomer liquid to a polycondensation reaction vessel and polymerizingthe transported part, and a process for newly supplying theester-forming acid component and the ester-forming diol component to theoligomer left in the esterification vessel to carry out theesterification.
 8. The method for producing the polyester compositionaccording to claim 7, wherein within 30 minutes after the finish of thetransportation of the oligomer liquid to the polycondensation reactionvessel, the ester-forming diol component at a temperature of not morethan 50° C. is supplied in an amount of 2 to 50 parts by weight per 100parts by weight of the transported oligomer liquid, and saidmetal-containing phosphorous compound is then added and thepolycondensation reaction is carried out.
 9. The method for producingthe polyester composition according to claim 8, wherein the temperatureof the oligomer after the addition of the ester-forming diol componentis lowered to a temperature lower by 30 to 50° C. than the melting pointof a pentamer in the oligomer liquid transported to the polycondensationreaction vessel, and said metal-containing phosphorous compound is thenadded.
 10. The method for producing the polyester composition accordingto claim 8 or claim 9, wherein an oligomer theoretical averagepolymerization degree calculated from an ester-forming diolcomponent/ester-forming acid component ratio in the polycondensationreaction vessel after the addition of the ester-forming diol componentis not more than
 5. 11. A polyester formed article obtained by formingthe polyester composition according to claim 1 or claim 2 into a fibrousor filmy shape.
 12. A polyester formed article obtained by bringing thepolyester formed article according to claim 11 into contact with a basiccompound to subject the polyester formed article to a weight reductiontreatment.
 13. The polyester formed product according to claim 12,wherein the polyester formed product has micropores on the surfacethereof.